Electron discharge device and method of manufacture



Sept. 6, 1949. w. c. DALE 2,48l202 ELECTRON DISCHARGE DEVICE ANID METHODOF MANUFACTURE Filed NOV. 26, 1946 Jo Z1 My, l Bu mmm 62M@ 0mm Q7(Ittorneg Patented Sept. 6, 1949 ELECTRON DISCHARGE DEVICE AND IMETHODOF MANUFACTURE William C. Dale, Livingston, N. J., assigner to RadioCorporation of America, a corporation of Delaware Application November26, 1946, Serial No. 712,267

5 Claims. 1

My invention relates to electron tubes, and more particularly to suchtubes in which the electron stream is required to traverse at least twogrid members, and to their manufacture.

The employment of a plurality of grids in elec-- tron tubes between thecathode and anode is associated with diliiculties which must be overcomein order to prevent impairment of tube characteristics. Thus intetrodes, for example, where a screen grid is interposed between theanode and control grid, there is a tendency for the electrons emanatingfrom the cathode to be absorbed by such screen grid and produceundesired current therein.

It has heretofore been recognized that the most effective way to shieldcertain grids in an electron tube from primary electrons is to align thegrid closest to the cathode, such as the control grid, which is usuallybiased slightly negative With respect to the cathode, with the turns ofthe other grid or grids following the control grid. To accomplish suchalignment it has been the practice to first mount one grid upon itssupport and then mount the other grid or grids upon their supports,after iirst manually adjusting their longitudinal positions so thattheir turns are in line in the direction of the electron travel from thecathode to the anode. However, such manual adjustment is not entirelysatisfactory for the reasons, among others, that it involves anundesirable time expenditure and is dependent upon the operatorsfaculties which may not always be reliable. The lack of reliability ofsuch manual adjustment is more pronounced in the manufacture of smallsized tubes where the parts are comparatively small and require a moreor less precise positioning.

It is, accordingly, the principal object of my invention to minimizeabsorption of electrons by one or more of a plurality of grids in anelectron tube, where such absorption would result in impairment of tubecharacteristics.

It is a more particular object of my invention to align the transversegrid wires of a plurality of grids in an electron tube in directionsnormal to the cathode, in an accurate manner and with a saving of time.

A further object of my invention is to support a plurality of gridmembers in an electron tube in such a manner that the support isaccomplished (Cl. Z50-27.5)

only when the grid members are in a predetermined longitudinal positionrequired for alignment of their transverse grid wires in directionsnormal to the tube axis.

Further objects of my invention will suggest themselves as thedescription proceeds.

While the scope of my invention is pointed out particularly in theappended claims, it may 'best be understood from the following detaileddescription of an embodiment thereof, taken in connection with theaccompanying drawing', in which Figure 1 shows an elevation partly insection of an electron tube having two grids made in accordance with myinvention with the turns thereof automatically aligned in assembly;

Figure 2 shows an elevation of one of the grids employed in the tubeillustrated in Figure l;

Figure 3 shows an elevation of the other of said grids which has largerlateral dimensions than the grid of Figure 2, permitting it to be placedover and surround said grid in coaxial relationship and at apredetermined distance therefrom;

Figures 4, 5, 6 and 7 show one way of making the grids illustrated inthe previous gures; Figure 4 showing the cutting of the rods to suitablelength; Figure 5 depicting the manner in which lateral extensions orswages are provided on the rods; Figure 6 illustrating the completedrod; and Figure 7 showing the step of applying transverse grid wires totwo of such rods and clearly indicating the function of the swages indetermining the longitudinal position on the rods of the firsttransverse grid wire,

Referring now to Figure 1, there is shown an electron tube having anenvelope It enclosing an electrode mount including cathode I I,flattened elliptical anode i2, shown in cross section, two grids I3, I4and two insulating spacers I5, I8 between which the electrodes aresupported. The tube is also provided with external contact pins I1. GridI3 has a pair of grid side rods I9 and grid I4 includes grid side rods2D. Grids I3, I4 are shown in Figures 1, 2 and 3 as having anaccentuated linear pitch for purposes of illustration.

In accordance with my invention grid side rods I9, 20 are provided withswages I8, each of which is provided with an upper and lower surface asviewed in Figure 1, normal to the side rods. The

first turn on each of grids I3 and I4 is applied to one of each pair ofsaid side rods I9, 20 beginning at a portion thereof longitudinallyspaced a predetermined distance X from the lower surfaces of swages I8.The grid-wire-turns on each of the grids referred to start at a commonside of cathode I I as shown in Figure l and observe a correspondinglinear pitch. The lower surface of each of swages I8 abuts against theupper surface of insulating spacer I6. Since this surface of spacer I6is planar the lower surfaces of swages I8 lie in a common, plane. Sincethe distance X represents longitudinal spacing of the point of beginningof the grid-turns on each of grids I3, I4 from the lower surfaces ofswages I8, these points of r beginning of said grid turns lieh in acommon plane. Since the turns of each gridarecharacter- ,ized by acorresponding linear pitch it follows that when grids I3, I4 are mountedin such -a manner that the lower surfaces of swages t8 abut the uppersurface of spacer I6, the grid turns of -one of the grids are in linewith the grid turns of the other grid substantially in `planes parallelto the direction, of the electron flow from the cathode to the anode.

The alignment of the turns of one grid with the turns off one or moreother grids in a common vdevi-ce is achieved according to my inventionto the extent that inherent :possibilities for such alignment exist in agiven structure. When planar grids are involved, which .arerectilinearly displaced, an actualalfignment of the turns thereof inpla-nes parallel to the direction of lelectr-on travel is accomplished.However when the grids are circular `or elliptical or -of flattenedelliptical cross 'section and -are -concentrically disposed actua-lalignment of the turns of several such grids throughout their :lengthsis inherently -impossible unless special recourses are availed of suchas modifying the epitch -of the turns in some of the grids in proximitytothe grid Aside -rods to balance the variation that such-structuretends to produce in the-grid turns -of several grids. However, while myinvention as applied to vcircular or elliptical grids results in-acrossing of the grid turns of one grid by the grid turns Iof Yano-thergrid, -such-crossing takes :place substantial-ly midway between the twoside rods where the value of the electron ystream vis "at v a maximum.The crossed turns describe sharp angles =as they diverge tow'a-rd theside --rodssuch divergence being rela.tively-slight yand being :at aminimum where alignment 'of the turns is-most needediand at a maximumwhere such alignment is -less significant. For shielding purposes,therefore, the alignment :produced -by my `invention is effective forgrids =of any type.

In carrying out ymy -inventionanydesired number of grids for use -in-acommon tube are -iirst prepared. Figures 2 .and A3 show two of suchgrids vhaving cross sections of such shape that the narrower gri-d ofFigure 4itis-adapted to -be -received within the wider grid of Figure 3.Although --for purposes of illustration grids -of such cross sectionalarea to per-mit concentric `relationship therebetween are`describedlhe-rein, it will be 'understood that my invention is equallywell adapted for use in "connection with -planar grids or grids of anycross sectional Yshape which employ side `rods for-supporting the gridturns. -As shown in Figures 2 and 3 notwithstanding -the diierence incross section normal to the longitudinal axis between the grids, the-longitudinal displacement along the `side rods fofY .the l:point ofbeginning of the lfirst fgr'id turn from the lower surfaces 2| of theswages I8, is represented by a similar value X for each of the grids.Moreover the linear pitch of the turns of grid I3 corresponds to thelinear pitch of the turns of grid I4. This linear pitch may be uniformas shown in Figures 2 and 3. It may also be non-uniform as for variablemu applications. However, such non-uniformity of linear pitch mustcorrespond in each of the grids, the turns of which are to be aligned.

As will be apparent from the foregoing, an important element in myinvention is the provision of swages I8 which provide a convenient datummeans for determining the location longi- -tudinally on the rods of thestart of the rst grid turn thereon. In the instant embodiment of myinvention a plurality of similar grid side rods, one of which is shownin Figure 6, are prepared as shown in Figures 4 and 5. Use is made oftwo cutting vmeans. '33, 34 shown in Figure 4 suitably spaced from eachother by a bar 35. This permits the successive cutting of a plurality ofrods having equal lengths. The cut rods are next subjected to a swagingoperation shown in Figure 5. This may be accomplished by square endedmembers 35,31 suitably spaced by rod 38. Instead of two swages, oneswage may be'applied to each rod without impairing its usefulness incarrying out the purposes of the invention. During the swfaging step therod is held against movement by members 3&3, 'ili and is pressed bymembers 36, 3l, by actuating means not shown, against anvils 4I, t2which are each provided with a rectangular recess having a lengthgreater than the diameter of the rod and a width substantially equal `tothat of yone'of said members 35, 3l.

Although the steps of cutting and swaging the side -rods shown inFigures'fi and v5 result in identical dimensioned grid side rods, thissimilarity of the rods is not essential for operativeness oftheinvention. For example, the rods 4may be of unequal length and theswages may be applied at differently spaced longitudinal locations onVseveral rods. The only critical dimensional requirement of the Arods isthat they possess a length from the llower 4surface 2l on swages AI'8 tothe far ends -of the'rods -suii'icient for bridging the axialdisplacement of the insulating spacers I6 and I'I shown in Figure 1 andfor support by said spacers.

The 'grids shown in Figures 2 and 3 owe their property of automaticalignment when mounted in a device such as is illustrated in Figure l,to the novel structure thereof according to the invention. As shown inFigure 7, this structure permits thestepfof winding a grid wire on thepreviously prepared grid side rods to provide eachof the gridsdepictedin Figures 2 and 3. Side rods I9 yare supported in iiixed spacedrelationship by chucks 22, v23 which are ,provided with suitablerecesses for receiving the -ends lof the rods. Chucks Y22, 23 may eac-hbe provided with two or more pairs of such recesses for accommodatinggrid rods successively in a plurality of diierent spaced relationshipsfor a plurality of differently cross-sectioned grids Aor a plurality ofchucks of the character of 22, 2.3 may be used, each having a pair ofrecesses differentlyspaced. The ends I9 are-so vpositioned that swagesI8 thereon `abut planar-surface -24 of chuck 22. Chucks 22'and 23 aresodisposed that they hold rod I9 perpendicular to the planarsurface 24.Although additional swages 25 are shown on rods I9 at the ends thereofremote Yfrom the ends on -which swages I8 are applied, such additionalswages may be omitted without .departing Afrom the invention.

Two side rods thus supported provide a fixed frame on which grid wiremay be wound. The grid winding st-ep may involve the use of a notchingwheel 26 for cutting a transverse groove in side rods I9. Grid wire isthreaded into said 'groove from a suitable wire source (not shown).Peening wheel 21 is then brought into operative :position to close thegroove referred to to embed a transverse portion of the wire therein. Topermit .this wire winding procedure, the chucks may be rotatable and thenotching and peening wheels 26 and 21 may be supported on xed supports,or the chucks may be xed and the wheels referred to may rotate aroundthe rods I9.

Notching wheel 26 is supported on a structure which includes arm 28, andpeening wheel 21 is associated with an arm 29. Arms 28 and 29 are-provided with a critical length from their free ends to adjacentsurfaces of wheels 26 and 21. The arms are also provided with planar endsurfaces 3l), 3| normal to their longitudinal axis. In operationsurfaces 30, 3I of arms 28, 29 abut against a portion of the planarsurface 24 of chuck 22. Therefore at the beginning of :a grid windingoperation wheels 26, 21 are spaced a predetermined distance from surface24. The first lturn of grid wire on rods I9 is, therefore, begun at apoint on one of the rods which is displaced normally from surface 24 andconsequently from surface 2l on swaging member I8, a predetermineddistance. The grid winding operation may be continued in known manneruntil the grid is completed.

It will be apparent from the foregoing that my invention provides anaccurate and 'automatic alignment of .the grid turns of a multi-gridstructure and eliminates the necessity for manual acljustments. It,therefore, accomplishes a saving in time in the manufacture of a devi-ceemploying the grid structure referred to, permitting .ia re- -duction incost while enhancing the operative eiliciency of the device.

While I have chosen one embodiment for the purpose of illustrating mayinvention, it is to be distinctly understood that my invention is notlimited thereto. Various modifications may be made in the embodimentdescribed without departing from my invention. For example my inventionmay be employed in connection with grids each having only one supportingside rod. I desire to include these and other modications as may suggestthemselves to persons skilled in the art within the scope of theappended claims.

What I claim as new is:

1. An electron tube having a cathode, an anode substantiallyco-extensive with said cathode, Iand at least two wound grids disposedbetween and parallel to said cathode and anode, said grids comprisingside rods supporting a plurality of turns of grid wire, two spacedparallel insulating plates for supporting said side rods, and uniformlateral projections on said side rods forming planar surfaces normal tosaid side rods, like planar surfaces on said rods being spaced equallyfrom the nrst turn of grid wire on each grid. the corresponding gridturns on each of said grids having a corresponding linear pitch Iandsaid like planar surf-aces abutting against a common surface of one ofsaid plates, whereby the turns of one grid are accurately aligned withthe turns of the other of said grids in planes normal to the cathode andanode and parallel to the direction of electron travel in said tube.

2. An electron tube having electrodes including a plurality of grids,said grids including side rods.

and at least one insulating plate for supporting one end of said siderods, at least one lateral projection on each of said side rods having aplanar surface normal to said rods engaging -a common surface of saidplate, the corresponding trans- Verse grid wires on each of said gridshaving correspondingly linear displacement along said rods, said planarsurface :being spaced a predetermined distance from the I'lrst of saidtransverse grid wires, whereby the grid wires on one grid areeffectively in line with the grid wires on another of said grids inpredetermined planes, for effective shielding of at least one of saidgrids by another of said grids.

3. An electron tube having at least a cathode, an anode and two grids,each of said grids including at least one side rod for supporting gridwires thereon, said grid wires being similarly spaced on said grids,like planar means on each of said at least one side rod equally spacedfrom the rst of said grid wires, and said planar means comprising aswage on said side rod having a planar surface normal to said rod,additional planar mean-s for supporting said rods with said like planarmeans thereon in the same plane and adjacent each other, whereby thegrid wires of one of said grids are effectively in line withcorresponding grid wires of the other of said grids in planes parallelto the direction of electron travel from said cathode to said anode.

4. An electron tube having at least a, cathode, an anode, and two grids,said grids having side rods for supporting a grid wire thereon, lateralprojections on said side rods forming planar surfaces normal Ito saidside rods, said grid wire extending transversely and longitudinally ofsaid side rods and being fixed thereto, the magnitude of longitudinalextension of said grid wire t0- wards one end of said rods -beingdetermined by certain of said planar surfaces, the longitudinal patternof said grid wire in one of said grids being similar to the longitudinalpattern of said grid wire in the other of said grids, and means forsupporting said grids with said certain of said surfaces in a commonplane and adjacent each other, .whereby one of said grids eiectivelyshields the other of said grids from electrons iiowing from the cathodeto the anode.

5. An electron tube having a cathode, an anode, at least two grids, andat least one insulating plate for supporting said grids, each of saidgrids having parallel transverse portions of correspomng longitudinaldisplacement, stop means on said grids having a planar surface normal,to the longitudinal axes of said grids and engaging a common surface ofsaid plate, the first of said parallel transverse portions on each 0fsaid grids being similarly spaced from said planar surrace 0f said stopmeans, whereby the parallel transverse portions of one of said grids areeffectively in line with the parallel transverse portions of the otherof said grids in planes parallel to the direction of Itravel ofelectrons from said cathode to said anode.

WILLIAM C. DALE.

REFERENCES CITED The following references le of this patent:

UNITED STATES PATENTS are of record in the

